wiggync

My battery is not charging and I had it tested and charged at my local parts store and it checked ok. I am thinking it could be the belt as the idler pulley was changed the day before I started having this problem. The belt felt tight enough but what is a rule of thumb to tell if it is too loose or too tight.

kjc

Did you put a voltmeter on the battery with the engine running? It should show at least 14 volts. If not, then you need to have them test that too. If it was a loose belt I think you'd hear it chirpin' when you put a strain on it.. like turning the steering wheel back and forth, or kickin' on the AC.

93gc40

Could also be the alternator or voltage regulator. Proper way to test tension on the belt is by use a a $5 tension gage. Deflection doesn't really work with serpentine belts.

hidetheid

13.2 to 14.4 with everything on and y do u think ur battery is not charging? The part store checked and said it was fine? U can't check a dead battery it needs to be charged... what is the issue

Gr85

get either a new battery, a new alternator, or a new coil, ..... or just replace em all...

wiggync

I had the battery charged and tested and they said it was fine. I was told to try starting it up and to disconnect the neg side of the battery and the motor shuts off when I do.

tjwalker

No, no, no! Never do this.

This is a very old school troubleshooting technique that may have been safe in 1970 for troubleshooting your AMC Gremlin, but it is not safe with your XJ. Spikes and transient voltage can occur and can result in damage to your alternator and your computer; both are susceptible to damage if you do this. Sometimes you get lucky and it doesn't happen. But the next time you can get burned.

Read this for confirmation.

http://www.troubleshooters.com/dont_...ct_battery.htm

Troubleshooting a charging system is relatively straight forward. It can usually be done by the owner with a meter and if you need further testing, take it to a shop.

wiggync

Wow thanks.. now I feel dumb.

tjwalker

Nope, not at all. Just file it under the category of "don't believe everything you hear"!

I'd share this information with whoever told you to do so as well, it may save them from an unnecessary repair in the future.

Getting back to your problem, if you have a voltage gauge on the dash, what does it read? With a healthy charging system and battery, it should be in the 13.5 to 14.0 volt range. If you don't have a gauge, you can get the same reading with a simple meter and one lead on each of the battery terminals with the meter on the DC Voltage setting.

Yes, it could be a loose belt, especially because the idler pulley was just replaced. The belt on the 4.0 engine needs to be awfully darn tight to work properly and stay quiet. Tighter than any other engine I've ever had. So you could try tightening it a smidgen. If you aren't good with how tight it should be by feel, get a gauge. I recomend the Krikit II tension gauge.

wiggync

It is reading 9volt on the dash. After the shop charged the battery it was reading 14 and it slowly goes down with every start.

tjwalker

Okay, with the battery passing a load test and with your 9 volt dash gauge reading, you have a charging system problem. Now to figure out why.

1. You MUST verify proper tightness on your belt. Can't proceed to step #2 until this is done.

2. Still symptomatic after belt verification? Have your alternator "bench tested" at a parts store. Beware though that bench testing is not always 100% conclusive.

Get on that belt tension verified first though. For sure. My gut tells me that whoever changed the idler pulley.....didn't tighten the belt enough. If this is a local shop, swing by and explain your symptoms to them. A good shop always stands behind their work.

wiggync

Ok, I had a friend change the idler pulley for me and he said it felt tight. I have my father in law bringing a tension gage tomorrow to test. Belt should be what 140-160?

wiggync

Ok, guess it was just chance. The problem was the alternator, had it bench checked and it was hardly putting out. Chnaged it and all is well now.

tjwalker

Glad you got it figured out. Relatively painless fix!